Cindy De Jonge receives an SNSF Starting Grant

Cindy De Jonge:
In this project, we want to develop tools to reconstruct past soil fertility. This will allow us to investigate changes in soil fertility on geological timescales (decades to millions of years), and determine the dependency between changing atmospheric CO₂, soil nutrient limitations and the capacity of soil to store carbon.

Currently, soils store a large fraction of the CO₂ emitted into the atmosphere. However, whether they will continue to do so in the future is unclear, as soil fertility potentially limits the amount of primary production (carbon fixation) and belowground carbon storage. A historical perspective, i.e. looking at past changes in soil fertility and carbon storage, can elucidate these processes on timescales that exceed experimental approaches (decades to millennia). In addition, by studying periods in the geological past with different climates, this allows us to track responses in soil fertility and soil carbon storage during periods of different atmospheric CO₂ concentrations.

As past soil fertility can’t be measured directly on old soils (paleosoils, or soil deposits), I will instead measure chemical fossils that reflect past microbial diversity. By quantifying these specific molecules, I want to reflect two main types of soil fertility; past soil mineral fertility, and nitrogen availability and cycling. After calibration in modern soils, these new tools are then measured in paleosoils, using time series to determine the impact of climate change and land use change, on soil fertility and the type and amount of soil carbon stored. Eventually, our findings can be used to know the limits and future behaviour of soil carbon, and potentially help with increasing this carbon sink to mitigate current climate change.